Cut-Off
Definition
The minimum analyte concentration that an SFSL reports as positive. SAMHSA-style serum cut-offs commonly used at Indian labs include morphine 2 ng/mL, cocaine 5 ng/mL and amphetamine 10 ng/mL. Urine cut-offs are typically one to two orders of magnitude higher.
- Function
- Minimum concentration reported as positive
- Morphine (serum)
- 2 ng/mL, SAMHSA-style Indian SFSL cut-off
- Cocaine (serum)
- 5 ng/mL
- Amphetamine (serum)
- 10 ng/mL
- Urine cut-offs
- Typically one to two orders of magnitude higher
Common questions
Why is a urine cut-off so much higher than a serum cut-off for the same drug?+
Urine concentrations reflect cumulative renal excretion and are usually far higher than the actively circulating serum level, so a urine assay needs a higher threshold to avoid flagging trace background levels as a true positive.
Does a result below the cut-off mean the drug is absent?+
No. It means the concentration is below the level the lab has validated for reliable reporting, not that the analyte is undetectable; a more sensitive confirmatory method could still show trace presence.
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